"The medium does things to people and they always completely unaware of this. They don’t really notice the new medium that is ruffing them up. They think of the old medium because the old medium is always the content of the new medium. As movies tend to be the content of TV and as books used to be the content, novels used to be the content of movies. So every time a new medium arrives, the old medium is the content and it is highly observable, highly noticeable. But the real roughing up and massaging is done by the new medium and it is ignored."